Spraying 



a rule, useless against fungi, and vice versa. Bearing 

 in mind what has been said regarding the nature of 

 fungus attacks and insect attacks, it should be clear 

 that the time for spraying against fungi is often just 

 before an imminent attack, e.g. in the case of potato 

 blight (due to Phytophthora infestans) about July 10, 

 whUe for insects the time is the first onset of the 

 attack. 



The best form for a spray is generally that of a 

 fine mist ; only rarely is it necessary or desirable 

 to apply a spray material so as to " wash " the plant 

 treated. Special machines have been devised for 

 the purpose of producing this type of spray. Its 

 formation depends mainly upon delivering the liquid 

 to be sprayed under sufficient pressure (generally 

 80 to 100 lb. to the square inch) through a suitable 

 nozzle which can be directed towards the thing 

 sprayed, and the direction of which can be easily 

 changed. A strong pump is therefore necessary, 

 and it is convenient if the material to be used can 

 be carried about in such a way as to be directly 

 available for the pump. 



For large areas large machines and powerful 

 pumps are required, but for ordinary gardens the 

 machines of the knapsack type are most convenient. 

 Knapsack spraying machines are of two kinds, the 

 continuous pumping and the pneumatic. In the 

 former the pump is worked during the whole time 

 the sprayer is in operation ; in the pneumatic', air is 



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